DEXAMETHASONE
Clinical safety rating: avoid
CYP3A4 inducers (eg phenytoin) may decrease efficacy and inhibitors may increase effects Can cause hyperglycemia and adrenal suppression with prolonged use.
Agonist at glucocorticoid receptors, leading to altered gene expression and suppression of inflammatory mediators.
| Metabolism | Primarily hepatic via CYP3A4; also metabolized by 11β-HSD2 in peripheral tissues. |
| Excretion | Primarily renal (65-80% as unchanged drug); minor biliary/fecal (<10%). |
| Half-life | Terminal elimination half-life 3-4 hours; clinically, duration of HPA suppression may exceed 24 hours due to prolonged receptor binding. |
| Protein binding | Approximately 77% bound to albumin; minor binding to corticosteroid-binding globulin. |
| Volume of Distribution | Vd ~0.8-1.0 L/kg; indicates extensive tissue distribution (crosses placenta, enters milk, penetrates CNS). |
| Bioavailability | Oral: 80-90%; IM: 80-100%; topical: negligible (systemic absorption <1% with intact skin). |
| Onset of Action | IV: rapid (minutes); oral: 1-2 hours; IM: 30-60 minutes; topical: variable (hours). |
| Duration of Action | Duration 36-54 hours (HPA suppression >24h with single dose); prolonged with higher doses or repeat administration. |
| Molecular Weight | 392.461 |
| Action Class | Glucocorticoids |
| Brand Substitutes | Decadron Tablet, Methasone Tablet, Decakem Tablet, Dexomet Tablet |
0.5-24 mg/day oral, IV, IM in 2-4 divided doses; anti-inflammatory: 0.75-9 mg/day; multiple myeloma: 40 mg oral/IV once daily on days 1-4, 9-12, 17-20 every 28 days.
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required for GFR <30 mL/min or dialysis; monitor for fluid retention. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid or use with caution, reduce dose by 75%. |
| Pediatric use | 0.08-0.3 mg/kg/day oral/IV/IM in 2-4 divided doses; asthma exacerbation: 0.6 mg/kg IV/IM (max 16 mg) once; croup: 0.6 mg/kg oral/IM once. |
| Geriatric use | Initiate at lowest effective dose; monitor for hyperglycemia, osteoporosis, and adrenal suppression; consider increased risk of fractures and infections. |
| 1st trimester | Limited studies suggest an increased risk of cleft palate (OR 3.35) with first-trimester exposure. Use only if benefit outweighs risk for severe maternal conditions. |
| 2nd trimester | Use with caution. May cause fetal adrenal suppression; monitor for intrauterine growth restriction with prolonged use. |
| 3rd trimester | Prolonged use may lead to neonatal adrenal suppression, hyperglycemia, or electrolyte abnormalities. Avoid unless necessary for maternal health. |
Clinical note
CYP3A4 inducers (eg phenytoin) may decrease efficacy and inhibitors may increase effects Can cause hyperglycemia and adrenal suppression with prolonged use.
| FDA category | Positive |
| Placental transfer | Crosses placenta readily; metabolized by placental 11β-HSD2 to inactive 11-keto form, but still reaches fetal circulation. |
■ FDA Black Box Warning
None required per FDA labeling.
| Serious Effects |
Systemic fungal infectionKnown hypersensitivity to dexamethasone or any component
| Precautions | Immunosuppression/increased infection risk, Adrenal suppression with prolonged use, Osteoporosis with long-term therapy, Hyperglycemia/diabetes exacerbation, Gastrointestinal perforation risk, Myopathy, Ocular effects (glaucoma, cataracts), Psychiatric disturbances |
| Food/Dietary | Limit high-sodium foods (processed snacks, canned soups) to reduce fluid retention. Avoid grapefruit and grapefruit juice as they increase dexamethasone levels via CYP3A4 inhibition. Increase potassium intake (bananas, spinach) if on loop diuretics. |
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| Breastfeeding |
| Enters breast milk in low quantities; peak milk concentration ~25% of maternal serum. No evidence of adverse effects in infants with short-term use. Less preferred than prednisolone due to longer half-life. |
| Lactation Rating | L2 (Probably compatible) |
| Teratogenic Risk | First trimester: Associated with increased risk of cleft palate (approximately 0.1-0.3% absolute risk above baseline). Second and third trimesters: May cause fetal adrenal suppression, growth restriction, and altered brain development. Chronic use increases risk of preterm birth and low birth weight. |
| Fetal Monitoring | Monitor maternal blood glucose, blood pressure, and signs of infection. Fetal surveillance: serial growth ultrasounds, amniotic fluid index, and fetal heart rate monitoring if prolonged use. Neonatal monitoring for adrenal insufficiency and hypoglycemia after delivery. |
| Fertility Effects | No direct effect on fertility. May suppress HPA axis, potentially altering menstrual cycles; used therapeutically in some fertility protocols (e.g., ovulation induction) due to anti-inflammatory effects. |
| Clinical Pearls |
| Intravenous dexamethasone causes perineal itching due to phosphate esters; warn patients. Taper after prolonged use (>3 weeks) to avoid adrenal crisis. Single dose of 10 mg may elevate INR in warfarin patients via CYP3A4 inhibition. Monitor blood glucose and potassium during therapy. |
| Patient Advice | Take with food or milk to reduce stomach upset. · Do not stop suddenly; follow taper schedule. · Report signs of infection (fever, sore throat) as steroid masks symptoms. · Avoid live vaccines during therapy. · Carry a steroid alert card if on long-term therapy. |